Introduce CaptureStateNotifier
This is a helper class for notifying a client of capture
state changes.
Bug: 146157104
Test: Compiles (further testing as part of the topic).
Merged-In: Ie27bc404805d319a6969290a6369d59fb68c1f38
Change-Id: I2902468c4692ba68e4bc9be0e5038d5505da7154
diff --git a/services/audiopolicy/service/CaptureStateNotifier.h b/services/audiopolicy/service/CaptureStateNotifier.h
new file mode 100644
index 0000000..4ca6601
--- /dev/null
+++ b/services/audiopolicy/service/CaptureStateNotifier.h
@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <mutex>
+#include <utils/StrongPointer.h>
+
+namespace android {
+namespace media {
+// Must be pre-declared, or else there isn't a good way to generate a header
+// library.
+class ICaptureStateListener;
+}
+
+// A utility for managing capture state change notifications.
+//
+// We are making some strong assumptions, for the sake of simplicity:
+// - There is no way to explicitly unregister listeners. The only way for a
+// listener to unregister is by dying.
+// - There's only at most one listener at a given time. Attempting to register
+// a second listener will cause a crash.
+// - This class isn't really meant to ever be destroyed. We expose a destructor
+// because it is convenient to use this class as a global instance or a member
+// of another class, but it will crash if destroyed while a listener is
+// registered.
+//
+// All of these assumptions can be lifted if there is ever a need.
+//
+// This class is thread-safe.
+class CaptureStateNotifier {
+public:
+ // Ctor.
+ // Accepts the initial active state.
+ explicit CaptureStateNotifier(bool initialActive);
+
+ // Register a listener to be notified of state changes.
+ // The current state is returned and from that point on any change will be
+ // notified of.
+ bool RegisterListener(const sp<media::ICaptureStateListener>& listener);
+
+ // Change the current capture state.
+ // Active means "actively capturing".
+ void setCaptureState(bool active);
+
+ // Dtor. Do not actually call at runtime. Will cause a crash if a listener
+ // is registered.
+ ~CaptureStateNotifier();
+
+private:
+ std::mutex mMutex;
+ sp<media::ICaptureStateListener> mListener;
+ bool mActive;
+
+ class DeathRecipient;
+
+ void binderDied();
+};
+
+} // namespace android